1.1 Field of the Invention
The present invention is directed to oxygenating compositions and methods for administering high levels of oxygen to subcutaneous and subepithelial tissues. In particular, methods for surface delivery of super oxygenating compositions for such treatment are described.
1.2 Description of Related Art
In many medical conditions including diabetes, burns, bedsores, and wounds the ability to oxygenate tissue is compromised and arterial oxygen may not reach damaged skin. Tens of thousands of patients die each year in the U.S. as a result of complications from insufficient delivery of oxygen to compromised tissue. Poor oxygen delivery, particularly in the limbs, results in slow healing, infections, scar development, and in the worst cases, tissue death and amputation.
The effect of oxygen tension on wound healing has been extensively studied. (For a review, see Whitney, J. D. (1989)). Wound healing is dependent upon several processes including proliferation of fibroblasts, collagen synthesis, angiogenesis and re-epithelialization. Animal studies have shown that several of these processes are affected by the subcutaneous partial pressure of oxygen (pO2). For example, supplemental oxygen can lead to increased rate of collagen deposition, epithelialization and improved healing of split thickness grafts. Increased subcutaneous pO2 has also been shown to improve bacterial defenses.
Many skin sores, ulcers, wounds and burns do not heal properly because there is a severe depletion of oxygen reaching these affected areas due to deterioration of the associated blood microcirculation. Conventionally, many of these skin diseases have been treated by various methods of administration of oxygen gas, either through inhalation of the gas, or by topical treatment with the gas.
The oldest method of administering oxygen gas to a patient is by hyperbaric chamber technology. This is a systemic treatment, involving placement of a patient in a closed pressurized chamber. Inside the chamber, the patient breathes elevated levels of oxygen gas. The extra oxygen taken in by inhalation becomes dissolved in the bloodstream and diffuses into the body tissues, thereby raising the local tissue oxygen levels. Unfortunately, hyperbaric treatment has not been successful in all situations, in particular where trauma or disease restrict blood flow to the affected tissue. Treatment of skin diseases by placing a patient in a hyperbaric chamber is costly and time-consuming and many patients react unfavorably when placed in hyperbaric chambers. Treatment of many conditions, such as bedsores, for much longer than four hours at one time may induce oxygen toxemia and hence be counterproductive. Toxic effects of hyperbaric treatment include twitching, ringing in the ears, dizziness, and in some cases severe effects such as coma and convulsions. Additionally, hyperbaric treatment is expensive and only available in treatment facilities that are properly equipped with hyperbaric chambers. Patients are only given oxygen through the lungs. The atmosphere of a multichamber hyperbaric unit is ordinary atmospheric gas as there is little known therapeutic value assigned to topical application of oxygen.
To overcome drawbacks associated with systemic hyperbaric treatment, attempts have been made to use xe2x80x9ctopical hyperbaricxe2x80x9d oxygenation devices designed for regional use on an isolated body part such as a limb. In such devices, the delivery route for the pressurized oxygen is topical, as opposed to systemic. Only the affected body part is exposed to the pressurized oxygen. Thus the oxygen gas must diffuse from the surface of the skin to the underlying tissues. For example, U.S. Pat. No. 4,801,291 discloses a portable topical hyperbaric apparatus having a gas impermeable internal chamber into which therapeutic gases are introduced to treat a portion of the patient""s body. Similarly, U.S. Pat. No. 5,020,579 discloses a hyperbaric oxygenation apparatus in which a limb is isolated in a portable chamber in the form of an inflatable bag into which oxygen gas is administered through an oxygen port in communication with a patient respirator connected to an oxygen source. The pressure of the oxygen in the collapsible bag is pulsated between maximum and minimum positive values. The patient cyclically experiences first an increase in the blood gas levels on the limb under treatment with a corresponding restriction in blood flow and, thereafter, a progressive return to normal blood flow rates in the limb as the pressure in the chamber changes from maximum to minimum positive pressure.
Several disadvantages exist with the approach of using xe2x80x9ctopical hyperbaricxe2x80x9d oxygenation devices. For example, an external oxygen source and a respirator normally used for respiratory therapy must be supplied with the apparatus. In addition, intermittent restriction and release of blood flow to the treatment area may not be advisable or tolerable for already compromised tissues.
Alternative topical methods to xe2x80x9ctopical hyperbaricxe2x80x9d treatments for poorly healing skin lesions involve the topical application of high levels of oxygen gas through wound dressings. U.S. Pat. No. 5,792,090, discloses an oxygen generating wound dressing and a method of increasing oxygen tension in surface wounds through the application of such a bandage. In this method, the wound dressing contains an oxygen permeable membrane and a reservoir capable of supplying oxygen through a chemical reaction. U.S. Pat. No. 5,855,570 describes another type of oxygen-producing bandage to promote healing of skin wounds. This device combines a wound dressing with an electrochemical, chemical, or thermal means of generating high purity oxygen, and can be regulated to supply oxygen gas to an area above the wound at various concentrations, pressures and dosages.
Unfortunately, topical treatments with oxygen gas such as by topical hyperbaric oxygenation and use of oxygen bandages have provided only minor improvements in promoting healing of skin disorders and in treating diseases. Moreover, peroxide application can generate singlet oxygen O2 and is a potential source of free radical damage to the skin (Elden, 1995).
Administration of elevated levels of systemic oxygen gas has been recognized as beneficial in the treatment of several skin disorders; however, the available delivery methods, such as hyperbaric chamber therapy, topical application of oxygen gas, topical hyperbaric treatment of isolated limbs and use of oxygen-producing bandages are at best minimally effective and often lead to problems that include toxicity and poor oxygen penetration of the skin. Currently used procedures for treatment of skin disorders such as ulcers, bedsores, and burns may exacerbate the existing skin disorder.
It is therefore desirable to provide methods of treatment for skin disorders that increase tissue oxygenation to induce more rapid healing of the skin, while not exacerbating an existing condition or causing additional side effects.
Conventional methods of increasing tissue oxygenation employ oxygen gas. In distinct contrast, the present invention discloses a novel method of increasing tissue oxygenation by topical application of a superoxygenated composition. The superoxygenated compositions rapidly raise oxygen partial pressure levels in the tissue by promoting efficient diffusion of oxygen into the tissue.
Accordingly, the invention discloses a method of increasing tissue oxygenation in mammals, comprising applying a superoxygenated composition to a tissue surface for a time sufficient to increase the subepithelial partial oxygen pressure from about 30% to about 120% above baseline pO2. The mammal will generally be a human, but there is no limitation to its use in veterinary applications to small and large animals that may have tissue damage responsive to therapeutic procedures that increase oxygenation of tissues.
The most common applications are direct application to the external skin but the method is equally applicable to mucous membrane surfaces of the alimentary canal as well as organ surfaces. Organs may be exposed or actually removed from the body cavity during surgical procedures. One may immerse an organ in a superoxygenated solution prepared in accordance with the invention, contact part of the organ with such a preparation, or perfuse the organ with the superoxygenated solution. In the latter case, this may be an ex vivo procedure intended to maintain organ viability and reduce ischemic damage.
One may desire to increase the oxygen level in tissues for several reasons, mainly in situations where the tissue is affected by a condition or disease such as bedsores, wounds, burns or ulcers or any condition that tends to decrease normal tissue oxygen levels. Additionally, It is expected to be particularly beneficial in treating anaerobic bacterial infections such as those caused by Pseudomonas species, Bacteroides species such as Bacteroides fragilis, Prevotella melaninogenica, Prevotella bivia, Prevotella disiens, Fusobacterium, Actinomyces, Lactobacillus, Propionibacterium, Eubacterium, Bifidobacterium, Arachnia, Peptostreptococcus, Veillonella, Clostridium species such as C. tetani, C. botulinum, C. perfringens, C. difficile and Porphyromonas. These infections may fester internally in lung tissue, oral or vaginal mucosa or become embedded in the surface of organs such as liver, kidney and heart.
Accordingly, one of the benefits of using the disclosed methods to enhance tissue oxygen levels is the toxicity to pathogenic anaerobic bacteria. A particularly desirable application is to control or kill the anaerobic bacteria responsible for peridontal disease. A superoxygenated mouthwash solution would be safe and convenient for use and can be packaged to maintain stability of the superoxygenated solution by using a pressurized container with means for single dose dispensing or packaged for single use.
The superoxygenated compositions of the present invention comprise at least about 55 ppm oxygen but find useful concentrations from about 45 to about 220 ppm. The oxygen level in the compositions depends on several factors, including the type of composition, the temperature, and other components, active or not, that may be added for various reasons such as stability, ease of application or to enhance absorption.
It is well known that gas concentration in fluids will be inversely proportional to the temperature. When desiring to use aqueous based superoxygenated compositions, the temperature will be dictated not by chemical considerations but by the potential damage to living tissue and by the need for higher oxygen concentrations. Accordingly, where the compositions are applied locally to external skin surfaces; for example to a forearm lesion, solution temperatures of about 0xc2x0 C. will generally be considered appropriate. This will provide relatively high oxygen levels, typically in the range of 220 ppm. On the other hand, a patient may be whole-body immersed in a whirlpool bath at a more comfortable temperature in the range of about 34xc2x0 C. The oxygen concentration will necessarily be less than 220 ppm due not only to temperature but also to the open environment commonly used in whirlpool baths in such establishments as rehabilitation centers.
The superoxygenated solutions and compositions of the present invention comprise oxygen microbubbles. Conventionally pressurized liquids such as carbonated beverages contain relatively large gas bubbles that escape fairly quickly into the atmosphere once pressure is released. The microbubbles employed in the disclosed compositions are much smaller, remain in solution longer and are thus more stable. Importantly, the oxygen provided by the microbubbles is at a partial pressure effective to quickly raise subepithelial oxygen partial pressure significantly above baseline or normal oxygen partial pressure levels.
As generated for use in the disclosed superoxygenated compositions, microbubble size is typically in the 1-2 micron range. The small size is believed to be an important contributor to the beneficial effects of topical application of solutions containing the microbubbles. The most preferred solutions appear to be those in which the oxygen bubbles are no larger than about 8 microns in size; however, a range of microbubble sizes exist in the prepared solutions, at least as small as 0.6 microns as detected at the limit of resolution by impedence methods for which results are illustrated graphically in FIG. 3. A practical range for many applications is between about 1xcexc and about 1xcexc in diameter or between about 3xcexc and about 8xcexc in diameter.
While the microbubble compositions need not be purely aqueous, compositions will normally comprise an aqueous base such as a buffer, or a pharmaceutically acceptable vehicle that will not be harmful if in contact with a tissue surface. Buffers, if employed, are preferably in the physiological pH range of 7.2-7.4 but may also be at lower pH such as provided by acetate buffers or at a higher pH in more alkaline buffers such as carbonate buffer. For many applications the superoxygenated compositions will comprise water and oxygen microbubbles.
It may be beneficial in some circumstances to provide agitation to the superoxygenated composition while it is being applied to the tissue. This will increase oxygen contact to the tissue surface and may increase efficiency of uptake. Agitation is inherent in the method of application when the compositions are part of a whirlpool bath treatment and may compensate somewhat for some decrease of oxygen in an open atmosphere environment and use of temperatures that are intended to provide patient comfort.
The oxygen supersaturated compositions of the invention may be applied in a variety of ways depending on the area to be applied, the nature of the condition and, for treatment purposes, the health condition of the subject or patient to be treated. Skin treatments will typically be applied as solutions that may be incorporated into creams, pastes, powders, ointments, lotions or gels or simply superoxygenated microbubble preparations in nonaqueous or aqueous media. An important consideration will be the concentration of microbubbles in the preparation and its ability to increase subepithelial partial oxygen pressure.
The method of application to the skin may be by soaking, immersion, spraying, rubbing or aerosols. The preparations may be applied to dressings that are in contact with the skin, such as plasters and wound coverings. In other applications, douches or enemas may be used for vaginal or rectal administration. Selection of the method will depend on particular patient needs, the area of application and type of equipment available for application.
Superoxygenated compositions are another aspect of the invention. The composition comprises an aqueous-based solution of oxygen microbubbles having a diameter of from about 0.6 micron to about 100 microns and having an oxygen concentration between about 45 ppm and about 220 ppm. Preferred embodiments include superoxygenated compositions where the microbubble diameter ranges from about 0.6 to about 5 microns and compositions where the microbubble diameter is about 5 to about 8 microns. A highly preferred superoxygenated composition includes microbubbles of oxygen in the range of 1-2 microns.
While liquid microbubble superoxygenated compositions will be preferred in most applications, the compositions may be in solid or frozen form. In aqueous based solutions this may be as low as xe2x88x9240xc2x0 C. but could be as low as xe2x88x9270xc2x0 C. in frozen gases such as carbon dioxide or in liquified gases such as nitrogen. These low temperatures are not practical for applications to living tissue; however, long term storage of certain cells or other biological material may benefit from this type of environment. In any event, there are several applications of superoxygenated aqueous solids in providing for example a slow release oxygen environment or where ice might be in contact with excised organs being transported for transplant purposes.
The compositions and methods disclosed may be combined in an apparatus for the purpose of providing a tissue oxygenating environment to a mammal in need of increased tissue oxygenation. An apparatus may include a container for holding an at least 55 ppm superoxygenated aqueous solution produced from an oxygen generating machine connected to the container. The apparatus may further include additional features for more efficient and convenient use, such as devices to agitate the superoxygenated composition being applied. In a particular embodiment, the device may induce a whirlpool effect. The device may be a sonicator to provide more effective distribution of microbubbles and which may help to maintain high oxygen levels in the solution. Stirrers, shakers, bubblers and the like may also be used to provide mixing.
The apparatus may also include a temperature controller that may be useful in controlling the oxygen levels in the superoxygenated solutions. An additional effect may be to enhance oxygen uptake through the skin of some subjects due to an increase in skin surface temperature. For use with patients, one may prefer to adjust temperatures to between about 37xc2x0 C. and about 45xc2x0 C.
In a particular application, the methods and compositions may be used to treat anaerobic infections. Generally this will involve applying any of the aforementioned compositions to a skin lesion suspected of harboring anaerobic bacteria. The method should be particularly effective against the anaerobic bacteria typically found in gangrenous or ulcerated tissue. Such anaerobic bacteria are also found in wound infections. Patients are likely to benefit from increased tissue oxygen in the wound area. Burned skin areas are particularly susceptible to infection, particularly where tissue is destroyed or badly damaged as in second and third degree burns. Burn patients are expected to benefit from such treatment that can be used prophylactically as well as therapeutically. Other conditions that will benefit from increased tissue oxidation include the soft tissue in the oral cavity, particularly in treating gum disease that is usually caused by anaerobic bacteria.
For convenience, kits may be used to package various superoxygenated compositions prepared in accordance with the invention. An exemplary kit with appropriate instructions for use in topically increasing tissue oxygenation may contain a sealed permeable flexible container and a containerized superoxgenated composition in one or more of the variations described. The kits may additionally include a whirlpool generating device, and/or a thermostat/heating device for adjusting temperature inside the container.
As discussed, the disclosed methods employ application of a superoxygenated composition to a surface for a time sufficient to increase the subepithelial tissue partial oxygen pressure (pO2) from about 30% to about 120% above baseline pO2 levels. The method is applicable particularly to humans who suffer from such conditions as tissue necrosis, bedsores, ulcers, burns or anaerobic infection.
The present invention addresses several of the problems encountered in attempts to develop therapies and treatments that increase topical availability of oxygen to tissues, particularly to the skin. Skin conditions, such as ulcers, bedsores, wounds, burns, and other serious dermatological problems may be treated by utilizing an aqueous solution charged with oxygen microbubbles applied directly to the skin. An important application is scar reduction where treatment may be used subsequent to scarring or on wounds, burns or surgical incisions to reduce scar formation. The methods are also applicable to increasing oxygen levels in infected surface tissues such as puncture wounds and soft tissue infections of the oral cavity.
It is well known that many types of skin sores, ulcers, wounds and burns do not heal properly because there is a severe depletion of oxygen reaching these affected areas due to degeneration or damage of the associated blood microcirculation. The human skin is at the terminus of the oxygen delivery system and exhibits signs of oxygen loss in a variety of pathological conditions. Degeneration of skin tissue is largely due to oxygen deprivation. Although the skin is exposed to the atmosphere, only a negligible amount of oxygen is actually absorbed. Increasing the level of oxygen absorbed by the skin directly results in increased healing rates of the skin.
The present invention utilizes a method of tissue superoxygenation that provides oxygen to tissue to aid in its healing and revitalization. Oxygen is provided to the tissue through microscopic bubbles and is present at a pressure many times that found in blood. The oxygen in the microbubbles can be transported through the skin when placed in contact with the skin. Such treatment increases the oxygen level in the interstitial fluids of the subepithelial and dermal tissues and is immediately available to the oxygen-depleted cells, thereby inducing more rapid healing. The disclosed procedures will aid in the prevention of gangrene formation and treatment of sepsis, decrease the need for amputations in diabetic patients, and help to heal bedsores, skin lacerations, burns and wounds. This type of treatment is more convenient to use and is much more affordable than existing methods of treatment for these conditions, such as a hyperbaric chamber.
The methods are useful not only in prevention of several skin disorders but also in cosmetic and pharmaceutical applications. Of particular interest to many teenagers and even adults are formulations that will benefit healthy skin while also promoting healing of common acne, a skin condition that may be disfiguring to a certain degree.
Superoxygenated compositions may also benefit victims suffering from smoke inhalation and damage from inhaled hot air. In such cases, the disclosed superoxygenated compositions are administered directly to the lung in order to increase oxygen concentration to the damaged cells. Such treatment may also be used to wash inhaled particulates from the lungs and can be administered in conjunction with antibiotic and anti-inflammatory drug solutions where indicated. The superoxygenated fluid can be used as a spray or intubated as a soaking solution to provide more controlled contact with the internal surface of the lung.
In like manner, internal injuries such as bullet wounds may benefit from being flushed with the superoxygenated fluids herein disclosed. This will be particularly useful for deep wounds where surgery is not indicated or in field situations where access to the wound is difficult. In such cases, the wound is flushed with the disclosed compositions to inhibit anaerobic infection and to provide supplemental oxygen to damaged tissue.
The superoxygenated compositions are typically aqueous solutions of oxygen microbubbles with diameters from about 0.1 to about 10 microns, preferably about 1 to about 8 microns and more preferably at least about 0.6 to about 8 microns with oxygen concentrations from about 45 ppm to about 220 ppm. In most applications the solutions will include microbubbles with a range of sizes, including less than 0.6 microns up through 1,2,3,4,5,6,7,8,9 and 10 microns and may contain larger microbubble sizes as microbubbles coalesce, depending on temperature. Of course the oxygen concentration will depend on the temperature of the liquid, typical oxygen concentrations being up to about 220 ppm at 2xc2x0 C. or about 118 ppm at 34xc2x0 C. These concentrations may be varied depending on the condition of the tissue surface to be treated, the type of tissue and the location of the tissue surface.
In special applications considerably higher oxygen concentrations may be desired; for example, well above 220 ppm. This may be achieved by preparing solutions of oxygen nanobubbles as small as 20-30 nanometers such as those described in association with flowing liquids across hydrophobic surfaces (Tyrrell and Attard, 2001). Nanobubbles are thought to be flat rather than round and to form closely packed, irregular networks that nearly completely cover hydrophobic surfaces. They appear to reform quickly after being distributed and are therefore quite stable. Regardless of how nanobubbles are produced, it is likely that concentrations of oxygen significantly higher than 250 ppm may be attained and will be useful in achieving high tissue oxygenation levels.
Oxygen microbubbles may be prepared in water or in a pharmaceutically acceptable vehicle. Physiological saline, various buffers, or compounds that increase wetting and porosity are examples of composition variations. In some cases, one may wish to add antibiotics, anti-inflammatory compounds or other drugs to the compositions in order to expedite healing or more effectively treat certain bacterial infections.
In certain applications, it may be desirable to administer superoxygenated compositions in the form of creams, lotions, gels or solids. Such formulations are well recognized and accessible to those skilled in the art. The superoxygenated compositions may also be maintained in a frozen state, for example for storage, or for use in treatments where ice can be conveniently applied to a tissue surface so that higher levels of oxygen can be consistently maintained. In a particularly important application, frozen or chilled superoxygenated compositions may be used for storage and transport of organs intended for transplantation. This may avoid or ameliorate anoxic conditions arising from severance of the organs from the normal blood supply. Frozen or chilled compositions will be especially beneficial for such tissues, both because enzymatic processes are retarded at the lower the temperature, and because at lower temperatures, higher levels of oxygen can be incorporated into the oxygenated compositions so that degradation is inhibited.
The superoxygenated compositions may be administered in several ways such as through tubes connected to flexible bags containing superoxygenated solution or in some applications by immersion of tissue in a bath containing the oxygenated solution. For dental applications in treating gum disease, administration by a device similar to a water pic is an effective method for topically administering suitable superoxygenated solutions. Certain applications benefit from mixing or agitating procedures so that fresh solution constantly bathes the tissue; for example, lavage procedures or whirlpool baths in which an affected limb is immersed.
In certain embodiments, an apparatus for providing a tissue oxygenating environment to a mammal in need of increased tissue oxygenation is also within the scope of the invention. Such an apparatus incorporates a machine for generating oxygen microbubbles that may be as simple as an oxygen cylinder connected to a pressurized vessel at pressures in the range of 90-110 psi and introducing oxygen gas into the vessel that holds a liquid such as water or other suitable water-based fluid. An oxygenator may also be used, generating about 50 psi. A tube or other exit from the vessel provides the oxygenated solution to the target tissue. Oxygen levels in the solution may be increased by agitating or sonicating the vessel. Ultrasonic equipment external to the flow intake and adaptations to control diffusion patterns in a vessel or a bath may also be employed.
It will be appreciated also that solution temperature will affect total oxygen concentration so that in alternative embodiments, the apparatus may incorporate any of a number of well known devices for controlling temperature such as thermostatted baths. Thus where applications are whole limb or body applications in open air as in a whirlpool bath, oxygen concentrations will not usually exceed about 55 ppm. For treatment of an internal epithelial lining, as in oral mucosal infections, cooler temperatures and correspondingly higher oxygen concentrations will be tolerable. Oxygen concentrations will vary depending on the method of application whether by soaking, immersion, spraying, rubbing or aerosols; however, in any event, the compositions contacting the affected tissue will have a significantly increased oxygen concentration in the range of at least about 45 ppm.
While most applications will utilize aqueous solutions, the inventors do not wish to be unduly limited since high oxygen concentrations may be achieved in nonaqueous or aqueous/organic solvents. Such solvents should be non-toxic and pharmacologically acceptable for human use. Perfluorocarbons are a particular example of non-aqueous solvents that might be useful. Other solvents include those that are water-miscible such as alcohols and glycols. In certain applications it may be convenient to use gel formulations such as hydrophilic gels formulated from alginates or carrageenans.
Other embodiments include kits that conveniently provide some form of the apparatus described above and will be useful for topically increasing tissue oxygenation. Exemplary kits may include a sealed permeable flexible container containing a superoxygenated composition and instructions for applying the composition to the tissue surface or skin requiring increased oxygenation. Optional kit components include a thermostat/heating device for adjusting temperature inside the container and an oxygen supply connectable with a pressurized vessel for mixing, agitating or sonicating an oxygenated fluid.